The brain chemistry underlying mental exhaustion.

Emily Underwood does a review of work by Wiehler et al. (open source) on the brain chemistry underlying mental fatigue, also describing several reservations expressed by other researchers. From her description:

The researchers divided 39 paid study participants into two groups, assigning one to a series of difficult cognitive tasks that were designed to induce mental exhaustion. In one, participants had to decide whether letters and numbers flashing on a computer screen in quick succession were green or red, uppercase or lowercase, and other variations. In another, volunteers had to remember whether a number matched one they’d seen three characters earlier...As the day dragged on, the researchers repeatedly measured cognitive fatigue by asking participants to make choices that required self-control—deciding to forgo cash that was immediately available so they could earn a larger amount later, for example. The group that had been assigned to more difficult tasks made about 10% more impulsive choices than the group with easier tasks, the researchers observed. At the same time, their glutamate levels rose by about 8% in the lateral prefrontal cortex—a pattern that did not show up in the other group...

Here is the Wiehler et al. abstract:  

Highlights

• Cognitive fatigue is explored with magnetic resonance spectroscopy during a workday 

• Hard cognitive work leads to glutamate accumulation in the lateral prefrontal cortex 

• The need for glutamate regulation reduces the control exerted over decision-making 

• Reduced control favors the choice of low-effort actions with short-term rewards

Summary

Behavioral activities that require control over automatic routines typically feel effortful and result in cognitive fatigue. Beyond subjective report, cognitive fatigue has been conceived as an inflated cost of cognitive control, objectified by more impulsive decisions. However, the origins of such control cost inflation with cognitive work are heavily debated. Here, we suggest a neuro-metabolic account: the cost would relate to the necessity of recycling potentially toxic substances accumulated during cognitive control exertion. We validated this account using magnetic resonance spectroscopy (MRS) to monitor brain metabolites throughout an approximate workday, during which two groups of participants performed either high-demand or low-demand cognitive control tasks, interleaved with economic decisions. Choice-related fatigue markers were only present in the high-demand group, with a reduction of pupil dilation during decision-making and a preference shift toward short-delay and little-effort options (a low-cost bias captured using computational modeling). At the end of the day, high-demand cognitive work resulted in higher glutamate concentration and glutamate/glutamine diffusion in a cognitive control brain region (lateral prefrontal cortex [lPFC]), relative to low-demand cognitive work and to a reference brain region (primary visual cortex [V1]). Taken together with previous fMRI data, these results support a neuro-metabolic model in which glutamate accumulation triggers a regulation mechanism that makes lPFC activation more costly, explaining why cognitive control is harder to mobilize after a strenuous workday.

Even novices intuit complex music theory,

Bridget Alex does a nice summary of work by Weis and Peretz showing that people without musical training naturally improvise melodies that have hallmarks of tunes composed by professionals. Most individuals follow the arcane rules of music composition, even those who are unaware those rules exist. Here is the research article abstract:

Humans spontaneously invent songs from an early age. Here, we exploit this natural inclination to probe implicit musical knowledge in 33 untrained and poor singers (amusia). Each sang 28 long improvisations as a response to a verbal prompt or a continuation of a melodic stem. To assess the extent to which each improvisation reflects tonality, which has been proposed to be a core organizational principle of musicality and which is present within most music traditions, we developed a new algorithm that compares a sung excerpt to a probability density function representing the tonal hierarchy of Western music. The results show signatures of tonality in both nonmusicians and individuals with congenital amusia, who have notorious difficulty performing musical tasks that require explicit responses and memory. The findings are a proof of concept that improvisation can serve as a novel, even enjoyable method for systematically measuring hidden aspects of musicality across the spectrum of musical ability.

Reproducability crisis in machine learning systems that inform immediate or future actions

I have by now accumulated a list of articles on a growing debate over naive scientists, especially social scientists, botching their research by using machine learning techniques they don't understand. They can't 'show their work' or provide enough information for others to reproduce their results. This article by Harrison is a short and succinct summary that includes links to other publications, and you should check out the article by Gibney in Nature Magazine.

Alcohol, neuronal plasticity, and mitochondrial trafficking

Hernandez and Kaun provide a nice description of work by Knabbe et al. with summary graphics. Here is the start of their text:

Consumption of alcohol creates a sense of euphoria, reduces inhibition, and increases sociability and impulsivity. The age at which alcohol is first experienced is a key factor contributing to the likelihood to misuse alcohol. However, the impacts of the first experience of alcohol on the molecules in the brain at these key developmental stages are not well understood. Knabbe et al. endeavored to address the neuromolecular alterations resulting from acute alcohol by combining hippocampal proteomics with somatosensory and motor cortex protein, dendrite, axon, and mitochondrial analysis in adolescent mice. Evidence from this array of preparations led to the hypothesis that alcohol disrupted mitochondrial trafficking, and using Drosophila they demonstrated a functional role for mitochondrial trafficking in cue-induced alcohol preference.

The cross-assay and cross-species approach outlined in Knabbe et al. proved to be an effective way of discovering how alcohol hijacks brain mechanisms. Animals from flies to humans maintain functionally consistent neurotransmitter systems, neural circuit mechanisms, and molecular pathways underlying reward.

And here is the abstract from Knabbe et al.:

Alcohol intoxication at early ages is a risk factor for the development of addictive behavior. To uncover neuronal molecular correlates of acute ethanol intoxication, we used stable-isotope-labeled mice combined with quantitative mass spectrometry to screen more than 2,000 hippocampal proteins, of which 72 changed synaptic abundance up to twofold after ethanol exposure. Among those were mitochondrial proteins and proteins important for neuronal morphology, including MAP6 and ankyrin-G. Based on these candidate proteins, we found acute and lasting molecular, cellular, and behavioral changes following a single intoxication in alcohol-naïve mice. Immunofluorescence analysis revealed a shortening of axon initial segments. Longitudinal two-photon in vivo imaging showed increased synaptic dynamics and mitochondrial trafficking in axons. Knockdown of mitochondrial trafficking in dopaminergic neurons abolished conditioned alcohol preference in Drosophila flies. This study introduces mitochondrial trafficking as a process implicated in reward learning and highlights the potential of high-resolution proteomics to identify cellular mechanisms relevant for addictive behavior.

A systematic review of microdosing - research on low dose psychedelics

I pass on the link to this review by Polito and Liknaitzky. Their abstract:

The use of low doses of psychedelic substances (microdosing) is attracting increasing interest. This systematic review summarises all empirical microdosing research to date, including a set of infrequently cited studies that took place prior to prohibition. Specifically, we reviewed 44 studies published between 1955 and 2021, and summarised reported effects across six categories: mood and mental health; wellbeing and attitude; cognition and creativity; personality; changes in conscious state; and neurobiology and physiology. Studies showed a wide range in risk of bias, depending on design, age, and other study characteristics. Laboratory studies found changes in pain perception, time perception, conscious state, and neurophysiology. Self-report studies found changes in cognitive processing and mental health. We review data related to expectation and placebo effects, but argue that claims that microdosing effects are largely due to expectancy are premature and possibly wrong. In addition, we attempt to clarify definitional inconsistencies in the microdosing literature by providing suggested dose ranges across different substances. Finally, we provide specific design suggestions to facilitate more rigorous future research.

Music training enhances auditory and linguistic processing.

From Neves et al.:  

Highlights

• Systematic review and meta-analysis of neurobehavioral effects of music training. 

• We ask whether music training shapes auditory-perceptual and linguistic skills. 

• Multivariate meta-analytic models are combined with narrative synthesis. 

• Music training has a positive effect on auditory and linguistic processing. 

• Our work informs research on plasticity, transfer, and music-based interventions.

Abstract

It is often claimed that music training improves auditory and linguistic skills. Results of individual studies are mixed, however, and most evidence is correlational, precluding inferences of causation. Here, we evaluated data from 62 longitudinal studies that examined whether music training programs affect behavioral and brain measures of auditory and linguistic processing (N = 3928). For the behavioral data, a multivariate meta-analysis revealed a small positive effect of music training on both auditory and linguistic measures, regardless of the type of assignment (random vs. non-random), training (instrumental vs. non-instrumental), and control group (active vs. passive). The trim-and-fill method provided suggestive evidence of publication bias, but meta-regression methods (PET-PEESE) did not. For the brain data, a narrative synthesis also documented benefits of music training, namely for measures of auditory processing and for measures of speech and prosody processing. Thus, the available literature provides evidence that music training produces small neurobehavioral enhancements in auditory and linguistic processing, although future studies are needed to confirm that such enhancements are not due to publication bias.

Old hearts learn new tricks

Nusinovich's summary in Science Magazine of work by Lerchenmüller et al.:

Aging-related diseases such as heart failure and other cardiovascular disorders are the leading causes of death in many countries, and they are becoming increasingly common worldwide as the number of older people increases. The ability of the heart to produce new cardiomyocytes decreases with age, which makes it more difficult to repair damage and increases the risk of heart failure. However, a study by Lerchenmüller et al. suggests that exercise may offer some help in this regard even if started late in life. The authors had previously reported that voluntary exercise can stimulate the generation of cardiomyocytes in young adult mouse hearts, and now they have also observed this phenomenon in aged animals.

Here is the results statement of the article:

Cardiomyogenesis was observed at a significantly higher frequency in exercised compared with sedentary aged hearts on the basis of the detection of mononucleated/diploid 15N-thymidine–labeled cardiomyocytes. No mononucleated/diploid 15N-thymidine–labeled cardiomyocyte was detected in sedentary aged mice. The annual rate of mononucleated/diploid 15N-thymidine–labeled cardiomyocytes in aged exercised mice was 2.3% per year. This compares with our previously reported annual rate of 7.5% in young exercised mice and 1.63% in young sedentary mice. Transcriptional profiling of young and aged exercised murine hearts and their sedentary controls revealed that exercise induces pathways related to circadian rhythm, irrespective of age. One known oscillating transcript, however, that was exclusively upregulated in aged exercised hearts, was isoform 1.4 of regulator of calcineurin, whose regulation and functional role were explored further.

Dissecting and improving motor skill acquisition in older adults

 From the introduction of Elvira et al. (open source):

We designed a study intended to identify (i) the main factors leading to differences in motor skill acquisition with aging and (ii) the effect of applying noninvasive brain stimulation during motor training. Comparing different components of motor skill acquisition in young and older adults, constituting the extremes of performance in this study, we found that the improvement of the sequence-tapping task is maximized by the early consolidation of the spatial properties of the sequence in memory (i.e., sequence order), leading to a reduced error of execution, and by the optimization of its temporal features (i.e., chunking). We found the consolidation of spatiotemporal features to occur early in training in young adults, suggesting the emergence of motor chunks to be a direct consequence of committing the sequence elements to memory. This process, seemingly less efficient in older adults, could be partially restored using atDCS by enabling the early consolidation of spatial features, allowing them to prioritize the increase of their speed of execution, ultimately leading to an earlier consolidation of motor chunks. This separate consolidation of spatial and temporal features seen in older adults suggests that the emergence of temporal patterns, commonly identified as motor chunks at a behavioral level, stem from the optimization of the execution of the motor sequence resulting from practice, which can occur only after the sequence order has been stored in memory.

Here is their abstract:

Practicing a previously unknown motor sequence often leads to the consolidation of motor chunks, which enable its accurate execution at increasing speeds. Recent imaging studies suggest the function of these structures to be more related to the encoding, storage, and retrieval of sequences rather than their sole execution. We found that optimal motor skill acquisition prioritizes the storage of the spatial features of the sequence in memory over its rapid execution early in training, as proposed by Hikosaka in 1999. This process, seemingly diminished in older adults, was partially restored by anodal transcranial direct current stimulation over the motor cortex, as shown by a sharp improvement in accuracy and an earlier yet gradual emergence of motor chunks. These results suggest that the emergence of motor chunks is preceded by the storage of the sequence in memory but is not its direct consequence; rather, these structures depend on, and result from, motor practice.

Motor learning without movement

Fascinating work from Kim et al. on the influence of the prediction errors that are essential in calibrating actions of our predictive minds:

Significance

Our brains control aspects of our movements without conscious awareness, allowing many of us to effortlessly pick up a glass of water or wave hello. Here, we demonstrate that this implicit motor system can learn to refine movements that we plan but ultimately decide not to perform. Participants planned to reach to a target but sometimes withheld these reaches while an animation simulated missing the target. Afterward, participants unknowingly reached opposite the direction of the apparent mistake, indicating that the implicit motor system had learned from the animated error. These findings indicate that movement is not strictly necessary for motor adaptation, and we can learn to update our actions without physically performing them.

Abstract

Prediction errors guide many forms of learning, providing teaching signals that help us improve our performance. Implicit motor adaptation, for instance, is thought to be driven by sensory prediction errors (SPEs), which occur when the expected and observed consequences of a movement differ. Traditionally, SPE computation is thought to require movement execution. However, recent work suggesting that the brain can generate sensory predictions based on motor imagery or planning alone calls this assumption into question. Here, by measuring implicit motor adaptation during a visuomotor task, we tested whether motor planning and well-timed sensory feedback are sufficient for adaptation. Human participants were cued to reach to a target and were, on a subset of trials, rapidly cued to withhold these movements. Errors displayed both on trials with and without movements induced single-trial adaptation. Learning following trials without movements persisted even when movement trials had never been paired with errors and when the direction of movement and sensory feedback trajectories were decoupled. These observations indicate that the brain can compute errors that drive implicit adaptation without generating overt movements, leading to the adaptation of motor commands that are not overtly produced.

Brain changes, or the absence thereof, associated with mindfulness training.

Richard Davidson and his collaborators (open source, with useful graphics) inject a note of sanity into evaluating widely reported claims of brain changes induced by mindfulness meditation techniques. They note in their introduction:

Findings from a few small studies have permeated popular media with the notion that a few weeks of training in mindfulness-based stress reduction (MBSR) can lead to measurable changes in brain structure and have been cited over 3200 times, combined. However, there is a lack of replication (conceptual or direct) or confirmatory analysis of these findings in a fully randomized trial. Moreover, a recent meta-analysis found that the proportion of high-quality publications in this domain have not improved over time, although there are a growing number of high-quality studies being conducted.

Their abstract:

Studies purporting to show changes in brain structure following the popular, 8-week mindfulness-based stress reduction (MBSR) course are widely referenced despite major methodological limitations. Here, we present findings from a large, combined dataset of two, three-arm randomized controlled trials with active and waitlist (WL) control groups. Meditation-naïve participants (n = 218) completed structural magnetic resonance imaging scans during two visits: baseline and postintervention period. After baseline, participants were randomly assigned to WL (n = 70), an 8-week MBSR program (n = 75), or a validated, matched active control (n = 73). We assessed changes in gray matter volume, gray matter density, and cortical thickness. In the largest and most rigorously controlled study to date, we failed to replicate prior findings and found no evidence that MBSR produced neuroplastic changes compared to either control group, either at the whole-brain level or in regions of interest drawn from prior MBSR studies.

Wolf attacks predict far-right voting

Under MindBlog's category of "random curious stuff" I couldn't resist passing on the following bit of quirky political analysis from von Hohenberg and Hager:

Does the return of large carnivores affect voting behavior? We study this question through the lens of wolf attacks on livestock. Sustained environmental conservation has allowed the wolf (Canis lupus) to make an impressive and unforeseen comeback across Central Europe in recent years. While lauded by conservationists, local residents often see the wolf as a threat to economic livelihoods, particularly those of farmers. As populists appear to exploit such sentiments, the wolf’s reemergence is a plausible source for far-right voting behavior. To test this hypothesis, we collect fine-grained spatial data on wolf attacks and construct a municipality-level panel in Germany. Using difference-in-differences models, we find that wolf attacks are accompanied by a significant rise in far-right voting behavior, while the Green party, if anything, suffers electoral losses. We buttress this finding using local-level survey data, which confirms a link between wolf attacks and negative sentiment toward environmental protection. To explore potential mechanisms, we analyze Twitter posts, election manifestos, and Facebook ads to show that far-right politicians frame the wolf as a threat to economic livelihoods.

Emotional contagion and prosocial behavior

Keysers et al. do an open source review of studies on emotional contagion and prosocial behavior in rodents, whose brain regions necessary for emotional contagion closely resemble those associated with human empathy:

Rats and mice show robust emotional contagion by aligning their fear and pain to that of others.

Brain regions necessary for emotional contagion in rodents closely resemble those associated with human empathy; understanding the biology of emotional contagion in rodents can thus shed light on the evolutionary origin and mechanisms of human empathy.

Cingulate area 24 in rats and mice contains emotional mirror neurons that map the emotions of others onto the witnesses’ own emotions.

Emotional contagion prepares animals to deal with threats by using others as sentinels; the fact that rodents approach individuals in distress facilitates such contagion.

In some conditions, rats and mice learn to prefer actions that benefit others, with notable individual differences. This effect depends on structures that overlap with those of emotional contagion.

Efficiently irrational: deciphering the riddle of human choice

Highlights of an open source article from Paul Glimcher:

A central question for decision-making scholars is: why are humans and animals so predictably inconsistent in their choices? In the language of economics, why are they irrational?

Data suggest that this reflects an optimal trade-off between the precision with which the brain represents the values of choices and the biological costs of that precision. Increasing representational precision may improve choice consistency, but the metabolic cost of increased precision is significant.

Given the cost of precision, the brain might use efficient value-encoding mechanisms that maximize informational content. Mathematical analyses suggest that a mechanism called divisive normalization approximates maximal efficiency per action potential in decision systems.

Behavioral studies appear to validate this claim. Inconsistencies produced by decision-makers can be well modeled as the byproduct of efficient divisive normalization mechanisms that maximize information while minimizing metabolic costs.

The End of the World is Just the Beginning

The title of this post repeats the title of Peter Zeihan's latest book, which I've just finished reading and found utterly fascinating and entertaining, in a gallows humor sort of way. During my awakening this morning my mind was generating words attempting to cook Zeihan's basic message down into a few sentences... Here they are:

In the new world that we are now entering America is one of the few countries that can both feed itself and make all the widgets that it needs. Together with its partners in the NAFTA alliance it is geographically and demographically secure, able to turn inwards and still maintain much of its population and lifestyle. Almost all other countries must either export or import energy, food, materials, or manufactured products. Free trade transport routes that have permitted this are crumbling as America continues its withdrawal from guaranteeing a world order formed to oppose a former Soviet Union that fell in 1990. As the level of global trade diminishes, most countries outside the North American group must reduce their population levels and living standards.

I was pointed to this book by listening to a Sam Harris "Makeing Sense" podcast titled titled "The End of Global Order," an interview with Peter Zeihand and Ian Bremmer. Zeihan integrates geopolitical and demographic perspectives to make a compelling case that that past few decades have been the best it will ever be in our lifetime, because our world is breaking apart. For the past seventy-five years we have been living a a perfect moment made possible by post World War II American fostering:

“an environment of global security so that any partner could go anywhere, anytime, interface with anyone, in any economic manner, participate in any supply chain and access any material input—all without needing a military escort. This butter side of the Americans’ guns-and-butter deal created what we today recognize as free trade. Globalization.”

But,

“Thirty years on from the Cold War’s end, the Americans have gone home. No one else has the military capacity to support global security, and from that, global trade. The American-led Order is giving way to Disorder. Global aging didn’t stop once we reached that perfect moment of growth...The global worker and consumer base is aging into mass retirement. In our rush to urbanize, no replacement generation was ever born...“The 2020s will see a collapse of consumption and production and investment and trade almost everywhere. Globalization will shatter into pieces. Some regional. Some national. Some smaller. It will be costly. It will make life slower. And above all, worse.”

Zeihan shows that the America and its partners in the NAFTA accord, Canada and Mexico, enjoy a "Geography of Success" and demographics that will render it vastly better off than the rest of the world.

Perhaps the oddest thing of our soon-to-be present is that while the Americans revel in their petty, internal squabbles, they will barely notice that elsewhere the world is ending!!! Lights will flicker and go dark. Famine’s leathery claws will dig deep and hold tight. Access to the inputs—financial and material and labor—that define the modern world will cease existing in sufficient quantity to make modernity possible. The story will be different everywhere, but the overarching theme will be unmistakable: the last seventy-five years long will be remembered as a golden age, and one that didn’t last nearly long enough at that.

In the introduction of his book, from which the above quotes are taken, Zeihan states that the book's real focus..

...is to map out what everything looks like on the other side of this change in condition. What are the new parameters of the possible? In a world deglobalized, what are the new Geographies of Success?

The book's introduction and epilogue are useful summaries, and you should check out the very instructive graphics provided on Zeihan's website.

NOTE!! ADDENDUM TO POST 11/13/22 I am obliged to pass on a critique of Zeihan's shocking China predictions that points out some blatant errors in his numbers: Debunking Peter Zeihan’s Shocking and Popular China Predictions

Widespread ripples synchronize human cortical activity during sleep, waking, and memory recall

I pass on the summaries of work by Dickey et al.:  

Significance

Different elements of a memory, or any mental event, are encoded in locations distributed across the cortex. A prominent hypothesis proposes that widespread networks are integrated with bursts of synchronized high-frequency oscillations called “ripples,” but evidence is limited. Here, using recordings inside the human brain, we show that ripples occur simultaneously in multiple lobes in both cortical hemispheres and the hippocampus, generally during sleep and waking, and especially during memory recall. Ripples phase-lock local cell firing and phase-synchronize with little decay between locations separated by up to 25 cm, enabling long-distance integration. Indeed, corippling sites have increased correlation of very-high-frequency activity which reflects cell firing. Thus, ripples may help bind information across the cortex in memory and other mental events.

Abstract

Declarative memory encoding, consolidation, and retrieval require the integration of elements encoded in widespread cortical locations. The mechanism whereby such “binding” of different components of mental events into unified representations occurs is unknown. The “binding-by-synchrony” theory proposes that distributed encoding areas are bound by synchronous oscillations enabling enhanced communication. However, evidence for such oscillations is sparse. Brief high-frequency oscillations (“ripples”) occur in the hippocampus and cortex and help organize memory recall and consolidation. Here, using intracranial recordings in humans, we report that these ∼70-ms-duration, 90-Hz ripples often couple (within ±500 ms), co-occur (≥ 25-ms overlap), and, crucially, phase-lock (have consistent phase lags) between widely distributed focal cortical locations during both sleep and waking, even between hemispheres. Cortical ripple co-occurrence is facilitated through activation across multiple sites, and phase locking increases with more cortical sites corippling. Ripples in all cortical areas co-occur with hippocampal ripples but do not phase-lock with them, further suggesting that cortico-cortical synchrony is mediated by cortico-cortical connections. Ripple phase lags vary across sleep nights, consistent with participation in different networks. During waking, we show that hippocampo-cortical and cortico-cortical coripples increase preceding successful delayed memory recall, when binding between the cue and response is essential. Ripples increase and phase-modulate unit firing, and coripples increase high-frequency correlations between areas, suggesting synchronized unit spiking facilitating information exchange. co-occurrence, phase synchrony, and high-frequency correlation are maintained with little decrement over very long distances (25 cm). Hippocampo-cortico-cortical coripples appear to possess the essential properties necessary to support binding by synchrony during memory retrieval and perhaps generally in cognition.

Restoring the aged brain with cerebrospinal fluid.

The transfer of blood plasma from young animals to old animals, has been shown to reverse aging changes in the brain, and now Iram et al. show in mice that infusions of young CSF cerebrospinal fluid (CSF) into the brains of aged animals promote oligodendrogenesis and improve memory function, and that fibroblast growth factor 17 (FGF17) is a key molecule that mediates these effects.

Recent understanding of how the systemic environment shapes the brain throughout life has led to numerous intervention strategies to slow brain ageing. Cerebrospinal fluid (CSF) makes up the immediate environment of brain cells, providing them with nourishing compounds. We discovered that infusing young CSF directly into aged brains improves memory function. Unbiased transcriptome analysis of the hippocampus identified oligodendrocytes to be most responsive to this rejuvenated CSF environment. We further showed that young CSF boosts oligodendrocyte progenitor cell (OPC) proliferation and differentiation in the aged hippocampus and in primary OPC cultures. Using SLAMseq to metabolically label nascent mRNA, we identified serum response factor (SRF), a transcription factor that drives actin cytoskeleton rearrangement, as a mediator of OPC proliferation following exposure to young CSF. With age, SRF expression decreases in hippocampal OPCs, and the pathway is induced by acute injection with young CSF. We screened for potential SRF activators in CSF and found that fibroblast growth factor 17 (Fgf17) infusion is sufficient to induce OPC proliferation and long-term memory consolidation in aged mice while Fgf17 blockade impairs cognition in young mice. These findings demonstrate the rejuvenating power of young CSF and identify Fgf17 as a key target to restore oligodendrocyte function in the ageing brain.

How the organization of generalized knowledge promotes memory.

From Wing et al.: Significance

What we remember is shaped by what we already know. For example, remembering the angelfish from a recent aquarium visit is easier for those who already know what angelfish are and know things about them. In addition to facilitating memory retrieval of specific items, prior knowledge also supports memory by providing an overarching organizational structure for new information. Here, we show how expert knowledge leads birdwatchers to organize birds based on conceptual features, in contrast to novices who organize birds based on perceptual features. In turn, experts’ organizational structure supports memory by reducing interference typically caused by high overlap among items, even when to-be-remembered birds were unfamiliar species. These findings demonstrate how the organization of generalized knowledge promotes memory.

Abstract

The influence of prior knowledge on memory is ubiquitous, making the specific mechanisms of this relationship difficult to disentangle. Here, we show that expert knowledge produces a fundamental shift in the way that interitem similarity (i.e., the perceived resemblance between items in a set) biases episodic recognition. Within a group of expert birdwatchers and matched controls, we characterized the psychological similarity space for a set of well-known local species and a set of less familiar, nonlocal species. In experts, interitem similarity was influenced most strongly by taxonomic features, whereas in controls, similarity judgments reflected bird color. In controls, perceived episodic oldness during a recognition memory task increased along with measures of global similarity between items, consistent with classic models of episodic recognition. Surprisingly, for experts, high global similarity did not drive oldness signals. Instead, for local birds memory tracked the availability of species-level name knowledge, whereas for nonlocal birds, it was mediated by the organization of generalized conceptual space. These findings demonstrate that episodic memory in experts can benefit from detailed subcategory knowledge, or, lacking that, from the overall relational structure of concepts. Expertise reshapes psychological similarity space, helping to resolve mnemonic separation challenges arising from high interitem overlap. Thus, even in the absence of knowledge about item-specific details or labels, the presence of generalized knowledge appears to support episodic recognition in domains of expertise by altering the typical relationship between psychological similarity and memory.

fNIRS - Functional near Iinfrared spectroscopy as a monitor of brain activity

Functional magnetic resonance imaging, or fMRI, requires that a subject remain still for an extended period within the confines of a large, noisy magnet available only at a dedicated facility. Sakai does an accessible review of recent work on functional near-infrared spectroscopy, or fNIRS, which affords a view into the brain based on blood oxygenation without the need for a big, immobile scanner. This optical imaging technique detects changes in how hemoglobin absorbs near-infrared light—usually wavelengths between 750 and 1,200 nanometers. Like fMRI, fNIRS provides an indirect measure of localized brain activity. It has now advanced from relatively simple measures of blood-oxygen changes to a sophisticated method of recording real-time brain responses associated with a wide variety of activities and cognitive tasks. fNIRS offers much better temporal resolution than fMRI, but light scattering limits fNIRS signals to the outer two centimeters of the brain, with a spatial resolution of about two to three centimeters—lower than fMRI but higher than EEG. The portability of fNIRS systems is allowing researchers to scrutinize the brain activity of subjects who are on the move, and observe brain changes associated with language recovery after a stroke.

Social Cognitive and Affective Neuroscience - a fascinating journal, many open source articles

Rather than charging in to do separate posts on several of the following fascinating articles, I pass them on for readers to click and choose abstracts and articles as they please.

Neural representation of the parent–child attachment from infancy to adulthood

Inter-brain synchronization is weakened by the introduction of external punishment border

Increased amygdala and decreased frontolimbic resting-state functional connectivity in children with aggressive behavior

Maladaptive self-focused attention and default mode network connectivity: a transdiagnostic investigation across social anxiety and body dysmorphic disorders

Neural correlates of negative emotion processing in subthreshold depression border

A multidimensional examination of psychopathy traits and gray matter volume in adults

Increasing self–other similarity modulates ethnic bias in sensorimotor resonance to others’ pain

Dynamic computation of value signals via a common neural network in multi-attribute decision-making

Stress in older adults accelerates immune system aging.

Seo does a summary article that points to the work of Klopak et al. The Klopak et al. abstract:  

Significance

As the world’s population of older adults increases, understanding disparities in age-related health is essential. Age-related changes in the immune system play a critical role in age-related morbidity and mortality. This study assesses associations between social stress and immunophenotypes as immune age phenotype markers for the first time in a national sample of older US adults. This study helps clarify mechanisms involved in accelerated development of the immune age phenotype, including socioeconomic and lifestyle factors and cytomegalovirus infection and reactivation. This study also identifies important points of intervention that may be useful in addressing inequalities in aging.

Abstract

Exposure to stress is a risk factor for poor health and accelerated aging. Immune aging, including declines in naïve and increases in terminally differentiated T cells, plays a role in immune health and tissue specific aging, and may contribute to elevated risk for poor health among those who experience high psychosocial stress. Past data have been limited in estimating the contribution of life stress to the development of accelerated immune aging and investigating mediators such as lifestyle and cytomegalovirus (CMV) infection. This study utilizes a national sample of 5,744 US adults over age 50 to assess the relationship of social stress (viz., everyday discrimination, stressful life events, lifetime discrimination, life trauma, and chronic stress) with flow cytometric estimates of immune aging, including naïve and terminally differentiated T cell percentages and the ratio of CD4+ to CD8+ cells. Experiencing life trauma and chronic stress was related to a lower percentage of CD4+ naïve cells. Discrimination and chronic stress were each associated with a greater percentage of terminally differentiated CD4+ cells. Stressful life events, high lifetime discrimination, and life trauma were related to a lower percentage of CD8+ naïve cells. Stressful life events, high lifetime discrimination, and chronic stress were associated with a higher percentage of terminally differentiated CD8+ cells. High lifetime discrimination and chronic stress were related to a lower CD4+:CD8+ ratio. Lifestyle factors and CMV seropositivity partially reduced these effects. Results identify psychosocial stress as a contributor to accelerating immune aging by decreasing naïve and increasing terminally differentiated T cells.